These pin and OK indicators are designed for use exclusively with Chubb fire extinguishers. The pin and OK indicator are a more secure and tidier option than the standard metal pin and tamper seal, with the added advantage that the plastic pin is not susceptible to corrosion. This is particularly beneficial for MED (Marine Equipment Directive) approved Chubb fire extinguishers and those located in areas where the extinguishers are exposed to water.